The present invention relates to dynamo electric machines and stators for use in same. More particularly, the invention relates to generally flat structured, dynamo electric machines, e.g., brushless electric motors, and to stators for use therein.
Brushless electric motors have been suggested and/or used for various purposes. In general, such motors come in at least two configurations; a drum style motor in which the rotor and stator of the motor have generally cylindrical shapes; and a flat style motor in which the rotor and stator of the motor are present as generally flat discs. Although the drum style motors are often capable of generating more power, the flat style motors have the advantage of being compact in size.
It would be advantageous to provide flat style or disc brushless electric motors which generate increased amounts of power.
Flat style brushless electric motors have been suggested for use with impeller pumps. See, for example, Mizobuchi et al U.S. Pat. No. 4,806,080; Kricker et al U.S. Pat. No. 5,332,374; and Atsumi U.S. Pat. No. 5,407,331. There continues to be a need to provide new impeller pumps driven by powerful flat style brushless electric pumps, in particular for pumping liquids, such as water and the like.
New dynamo electric machines, stators for use in such machines and pumps including such stators have been discovered. The present invention takes advantage of the discovery that dynamo electric machine stators comprising masses of metal particles, preferably pressed metal particles, provide more efficient, powerful dynamo electric machines, preferably brushless electric motors having longer useful lives and/or producing increased or enhanced amounts of power, relative to similar machines having substantially the same dimensions and including stators made from solid metal members.
Without wishing to limit the invention to any particular theory of operation, it is believed that the present stators which comprise masses of metal particles are effective in disrupting, or otherwise mitigating against the harmful effects of, eddy currents that develop in the stator. Such eddy currents reduce the effectiveness of the dynamo electric machines, for example, the effective power generating ability of the brushless electric motor. In any event, the present dynamo electric machines, including stators comprising masses of metal particles, have been found to be powerful and effective in many applications.
The present stators are useful in any dynamo electric machines, for example, motors, generators, alternators, motor/generator combinations, motor/tachometer combinations, frequency changers and the like. Preferably the dynamo electric machine is of the brushless type, and more preferably of the brushless direct current (DC) type. The term xe2x80x9cmotorxe2x80x9d is used extensively hereinafter and is meant to encompass or include within its scope any such dynamo electric machine.
One particularly useful application of such stators is in brushless electric motors which power work components, such as pump and compressor impellers, fan blades, mixing and blending implements and the like. A very advantageous configuration provides such stators used in combination with rotors which are integral with the work component. Pumps, such as liquid handling pumps, powered by such brushless electric motors are very beneficial embodiments of the apparatus of the present invention.
The present motors, stators, apparatus and pumps are relatively straightforward in construction and easy to use. These motors, stators, apparatus and pumps provide a high degree of reliability and long effective life and provide one or more advantages which enhance performance and/or cost effectiveness.
In one embodiment, the present invention is directed to motors (dynamo electric machines), preferably brushless electric motors, which comprise a rotor and a stator. The rotor has a rotary axis and includes a plurality of permanent magnetic poles arranged in a generally flat array. The stator, which comprises a mass of metal particles, preferably a mass of pressed metal particles, is spaced apart from and generally facing the generally flat array of permanent magnetic poles. The stator has a plurality of magnetic windings positioned and adapted to effect rotation of the rotor about the rotary axis upon energization thereof.
Reduced eddy currents preferably are obtained during operation of such motors relative to the operation of similar motors in which the stator comprises a solid metal mass or member instead of the mass of pressed metal particles. In addition, when compared to stator bodies made solely of polymeric materials, the present stator bodies provide motors with reduced effective air gaps between the stators and the rotors, which feature ultimately yields more powerful motors relative to similar motors with stator bodies of polymeric materials. The present stators preferably consist essentially of a mass of pressed metal particles. The mass of pressed metal particles advantageously has a density equal to at least about 95% of the theoretical density of a solid metal member. In a very useful embodiment, the stator includes substantially linear acicular metal particles having a substantially triangular configuration.
The present motors preferably are brushless direct current (DC) electric motors, for example, brushless DC, one (1), two (2) or more, such as three (3), phase electric motors.
The present stators preferably comprise plates, for example, substantially flat plates, and a plurality of spaced apart projections or teeth including masses of metal particles, for example, as described herein. The plates of the present stators have a first end surface, a substantially opposing second end surface and a peripheral surface therebetween. The plurality of spaced apart projections extend from the second end surface away from the plate and, together with the second end surface of the plate, define a plurality of slots therebetween.
The plate preferably has a central axis which intersects both the first end surface and the second end surface. Each of the plurality of projections preferably extends inwardly from the peripheral surface and terminates prior to intercepting the central axis.
Each slot of the plurality of slots preferably has a substantially constant dimension between the two adjacent projections which define the slot. In a very useful embodiment, the plate and projections are unitary, that is are made of a single or unitary member.
Apparatus for performing useful work are provided which comprise work components, rotors and stators. The work components, such as pump or compressor impellers, fan blades, mixing and blending implements, others assemblies which perform useful work on a material in contact with the work component and the like, include a rotary axis and are mounted for rotation about the rotary axis. The work component is configured and positioned so that the rotation of the work component is effective to perform work on a material in contact with the work component. The rotor is coupled, preferably directly coupled, to and rotatable with the work component and includes a plurality of permanent magnetic poles arranged in a generally flat array. The stator is as described previously and is adapted to effect rotation of the rotor and the work component upon energization thereof.
As used herein, the term xe2x80x9cdirectly coupledxe2x80x9d as it relates to the relationship between the work component and the rotor refers to an apparatus in which the work component and the rotor are directly secured or attached to each other, so that no power transmission assembly, for example, a shaft, gear arrangement or the like, transfers power from the rotor to the work component. This xe2x80x9cdirect couplingxe2x80x9d relationship, which may be considered an integral rotor/working component combination, very effectively provides power to the work component while reducing the size and space requirements of the apparatus.
In a very useful embodiment, the work component and stator are present in a unitary or single member, for example, a member made of a substantially uniform composition.
Pumps are provided which comprise pump casings, impellers, rotors and stators. The pump casing has an inlet and an outlet. The impeller has a rotary axis and rotatably mounted within the pump casing for rotation about the rotary axis. The impeller is configured and positioned relative to the pump casing so that rotation of the impeller is effective to urge fluid from the inlet to flow through the outlet. The rotor is coupled to and rotatable with the impeller and includes a plurality of permanent magnetic poles arranged in a generally flat array. The stator is as described previously and is adapted to effect rotation of the rotor and the impeller upon energization thereof.
The present work apparatus and pumps preferably provide increased or enhanced power, and more preferably reduced detrimental eddy current effects, during operation relative to similar apparatus and pumps in which a solid metal mass or member is used in place of the mass of metal particles in the stator.
Each of the features disclosed herein is included within the scope of the present invention. In addition, all combinations of the presently disclosed features which are not mutually inconsistent or incompatible are also included within the scope of the present invention.
These and other aspects and advantages of the present invention are apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.